methods for abstract pool (#419)

* include method to list current pool relays connections and to close all connections

* fix prettier

abstract-pool.ts

@@ -208,4 +208,16 @@ export class AbstractSimplePool {
       return r.publish(event)
     })
   }
+
+  listConnectionStatus(): Map<string, boolean> {
+    const map = new Map<string, boolean>()
+    this.relays.forEach((relay, url) => map.set(url, relay.connected))
+
+    return map
+  }
+
+  destroy(): void {
+    this.relays.forEach(conn => conn.close())
+    this.relays = new Map()
+  }
 }